Color Dodge

Blending the base layer with an exact but inverted copy of itself results in an all-white image However, apply a little Gaussian blur to the picture and things become a little more interesting Because blacks are preserved, using a small Gaussian blur radius with an inverted copy of the image will result in a line-drawing effect Color Dodge therefore allows you to build your own Find Edges filter that to some extent you can fine-tune afterward by increasing the blur Once it's applied, you can control its strength by reducing the layer's opacity However, you can't reverse the blur itself unless you step back through the History or use the History brush So, add Gaussian blur a little at a time and build up the line-drawing effect until you've created the desired result

Color. Dodge

Background

Color Dodge is the third of the Lighten group of blending modes—it's also my favorite member of the group because it's the only one that preserves blacks. Color Dodge inspects each color channel and then brightens the base color to reflect the blend color by decreasing the contrast; in fact, it's the exact opposite of Color Burn (see pages 30-31). However, one aspect of Color Dodge's definition is misleading. This is where it refers to "decreasing the contrast," because, just like dragging the Levels' white point, selecting Color Dodge actually increases the overall contrast of the image.

Rather than focusing on this strict "textbook" definition, remember that what Color Dodge actually does is lighten the image and increase contrast in brighter areas, while preserving the blacks.

KEYBOARD SHORTCUT

Windows: Alt+Shift+D Mac: Option+Shift+D

Layers Channels J Paths

A self-blend with Color Dodge lightens the image but retains the blacks.

Background

Background

Applying Color Dodge plus a little blur to an inverted image produces a line drawing.

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Desaturating

As you increase the blend layer's Gaussian blur, Color Dodge makes some partial reversals The original image's highlights become dark in the inverted layer, and are ignored, while the rest of the image is brightened m i * jA- V v^- ■

As well as simply inverting and blurring the blend layer, try desaturating it. Alternatively, you can always toggle between a negative and a positive view with Ctrl/Cmd-I

B'B

Layers Channels ^ Paths

Color Dodge - jOpacity: j 100% ►

Lock: ii ri 100°^►

Color Dodge + Blur 4- Invert

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^-y ^ Background Q

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Color Dodge ignores the blacks in the inverted blend layer.

Sometimes unexpected details can emerge from experimenting—here, I had no idea that there were reflections of text in the window.